Determinants of Difficult‐to‐Manage and Treatment‐Refractory Axial Spondyloarthritis: A Cross‐Sectional Analysis Within a Longitudinal Cohort

OBJECTIVE: The purpose of this study was to estimate the prevalence of difficult-to-manage (D2M) and treatment-refractory (TR) axial spondyloarthritis (axSpA) and to identify factors associated with D2M and TR disease in a longitudinal cohort. METHODS: We performed a cross-sectional analysis on data from the Schroeder Arthritis Institute Spondylitis Program cohort. Assessment of SpondyloArthritis International Society (ASAS) definitions for D2M and TR disease were applied to patients with axSpA. Sociodemographic and disease-related characteristics were compared between groups, and multivariable logistic regression was performed to estimate odds ratios (ORs) for factors associated with D2M. RESULTS: Among 536 patients, 49 (9.1%) met the ASAS D2M definition and 12 (2.2%) were classified as having TR axSpA. Compared with patients with non-D2M axSpA, those with D2M axSpA exhibited higher disease activity, worse function and spinal mobility, and a higher prevalence of comorbidities, degenerative spine disease, and fibromyalgia. patients with TR axSpA showed greater disease burden and more often were male, were HLA-B27-positive, and had radiographic axSpA, but they were less affected by noninflammatory pain contributors. In multivariable analysis, higher spinal pain scores (OR 1.48 [95% confidence interval (CI) 1.29-1.70]) and fibromyalgia (OR 3.09 [95% CI 1.33-7.15]) were independently associated with D2M. CONCLUSION: Approximately 1 in 10 patients with axSpA in this cohort fulfilled the ASAS D2M definition, with a smaller proportion classified as having TR axSpA. D2M status was associated with higher spinal pain and fibromyalgia, whereas patients with TR axSpA had active disease with fewer noninflammatory pain contributors. These findings support the clinical relevance of the D2M construct and highlight the need for a tailored management approach in clinical practice.